Generator regulator



Patented Oct. 28, 1952 GENERATOR REGULATOR- Brooks H. Short, Raymond A. Wilkins, and George B. Shaw, Anderson, and John W. Dyer, Pendleton, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Dela- Ware Application February 19, 1949, Serial N 0. 77,412

This invention relates to an electric current generating system for use on automotive vehicles and comprising an A. C. generator driven by the vehicle propelling engine and connected with a rectifier which puts out current for charging a storage battery and for other purposes. Heretofore, in systems of this type, the field current for the generator is provided by the rectifier at voltage which is relatively low, for example that required for charginga l2-volt storage battery. Since field voltage is low, the field winding is made of relatively heavy wire. The field winding, therefore, occupies considerable space.

An object of the invention is to efiect field excitation With a field winding which occupies less space than in the case of the generator referred to and to provide for field current regulation by the use of a thermionic tube available on the market. To do this, we provide for field excitation by a relatively high voltage source so that, by using a field coil having a sufiicient number of turnsof relatively fine wire, adequate field excitation can be eifected with relatively low field current and an available thermionic tube can handle this relatively low current. For controlling the conductivity of the tube we provide control of its grid bias through means which senses the relation between a voltage derived from the rectifier output terminal and the voltage of a standard D. C. voltage source.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanyingdrawing, wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

The figure is a wiring diagram of the invention.

Referring to the figure, a generator I0, having a fixed stator comprising coils I I, I2 and I3, has a rotating field excited by a coil I5 driven by a variable speed power source such as the engine of an automotive vehicle. The ends of coil I5 are connected with slip rings I6 and I1 engaged by brushes I8 and I9 respectively. A rectifier 29 is connected with coils II, I2 and I3 for A. C. input and with terminals 2i and 22 for D. C. output. Wires 23 and 24 are connected with terminals 2I and 22 respectively and normally with the input terminals 25 and 26 of a D. C. transformer or power pack 30 through normally engaged switch contacts 4|, 42, 43. Power pack 39 has output terminals 28 and 2! normally connected by normally engaged switch contacts 44, 45, 46 and 41, 48, 49, respectively, with wires +3 and B, respectively, whose potential difference is, for ex- 1 Claim. (Cl. 322-28) ample, 699 volts D. C. The contacts 4I49 are part of a relay switch 59 havinga magnet coil 40 connected with wires 23 and 24 and an armature 5i which is lifted by magnetic pull effected by coil 49 when the generator output voltage rises:

to a certain value corresponding to a. certain engine speed. The rise of armature 5I interrupts the input and output circuits of the power pack 39 and connects through closed contacts 54, 45,

59 and closed contacts 51, 48, 59, the wires +3 and B with wires 53 and 55, respectively; connected with the output terminals of a second power pack Ell Whose input terminals are connected with the secondary winding 6! of a transformer T having a primary Winding connected With stator coil I3. Pack 69 puts out 600 volts D. C.

Wire +B connects contacts 49, 56 with a terminal l I. Wire -B connects contacts 49, 59 with a terminal I2. Terminals II and I2 are, respectively, the most positive and most negative ends of two potentiometers or voltage dividers 69 and 70. Divider 69 includes a fixed resistance it, a junction 14 and a pentode tube "i8. Divider I0 includes a fixed resistance 75, a junction I3 and a voltage control tube TI which causes the voltage between junction 13 and terminal I2 to be fixed at 150 volts, for example, for a purpose to be described.

Plate 19 and cathode of tube I8 are connected, respectively, with terminals I4 and '12. Its stabilizing grids BI and 82 are connected, respectively, with terminals I2 and I3. Its control grid 83 is connected with a grid biasing control circuit senses the relation between generator output voltage and the voltage of a standard D. C. voltage source. This circuit comprises grid 83, wire 84, fixed potential D. C. source 85 and a .potentiometer comprisinga rheostat Wiper 8B and resistance 81 connected with wires 23 and 24. Wire 24 is connected by wire 12a, wire B and terminal 72 with cathode 89 which therefore has a fixed negative potential.

The circuit of the field coil I5, indicated by fine parallel lines, comprises triode tubes 90 in parallel and having their plates 9I connected by wire 92 with brush I8 and having their cathodes 93- connected by wire 94 with terminal I3. Terminal II is connected by wire 96 with brush I9. The tube 1! maintains cathodes 93 at 150 volts above the most negative terminal I2.

The grids of tubes 90 are connected by wire 99 with terminal 14 Whose potential varies in accordance with the conductivity of tube 18 which senses the change in the relation of rectifier output voltage to the voltage of the standard or fixed D. C. voltage source 85.

Let Cl represent the potential of grid 83, C2 the potential of terminal 14 and C3 the potential of terminal 13 and cathodes 93 which is fixed. Assume that the generator voltage output is to be held at a value such that voltage at the wiper 86 is 6 volts D. C. Cl will be 2 volts since source 85 provides -8 Volts at wire '84. When rid 83 has -2 volts bias, C2 has a value such that tubes 90, whose plate potential is around 450 volts, will pass current I2 to field coil of a value such that generator output voltage causes the potential of wiper 86 to be 6 volts D. C. When, due to increase in speed, the potential of wiper 86 increases to 6.5 volts, for example, potential Cl is *1.5 volts and hence has become more positive. Tube 18 is more conducting, I1 (current in resistance 16) increases and potential C2 decreases positively relative to C3, the potential of cathodes 93. Therefore bias on grids 95 has increased negatively and tubes 90 are less conducting and 12 decreases to lower fieldexcitation to a. value such that the generator, when operating at increased speed, will not cause the voltage at wiper 86 to be more than 6 volts. D. C.

When, due to decrease in speed, the voltage at wiper 86 decreases to 5.5 volts, for example, potential CI is 2.5'volts. Tube 18 is less conducting,.I1 decreases and potential C2 increases positively relative to C3, the potential of cathodes 93, and the bias on grid 95 increases positively and. tubes 90 pass more current so that the generator voltage is such that, at lower generator speed, the voltage at wiper 86 is 6 volts D. C.

As the tube 1'! must be kept in operation regardless of decrease of field current to a low value at high generator speed, the resistance which by-passes the field winding I5 passes suificient current to the tube 1! to maintain its operation.

Storage battery I60 is connected by a manual operated switch IOI. Battery H10 operates in conjunction with the power pack 39 initially to provide the current source for field excitation so that the generator output will reach 6 volts D. C. at relatively low engine speed. Then the relay switch 50 operates to change the connections with wires +3 and -B from the power pack 30 to the power pack 60 operated by the generator and operating to put out 600 volts D. C. at all generator speeds. above thespeed at which therelay switch 50 cuts in the pack 60.

When the engine is idling as frequently'happens in citydelivery service, the idle speed voltage of generator coil I3 will be sufficient for operation of the pack 60 to provide 600 volts D. C. in order to maintain 6 volts D. C. output at idle speed.

as herein disclosed, constitutes a preferred form,

it is to be understood that other forms might be adopted.

What is claimed isas follows:

An electric current generating system for use" 4 on automotive vehicles and comprising an A. C. generator driven at different speeds by the vehicle propelling engine, a rectifier connected with the generator for supplying direct current to a storage battery and other purposes, a D. C. source of relatively high voltage for supplying generator field excitation current, said generator having a field winding of sufficient number of turns of relatively fine wire whereby required field excitation can be effected with relatively low current, a first voltage divider connected across the terminals of field exciting D. C. source and comprising, in series, a resistance connected with the positive terminal of said D. C. source, a junction and a thermionic tube whose plate is connected with the junction and whose cathode is connected with the negative terminal of said D. C. source, a connection between the negative terminal of the rectifier and said cathode to maintain it at a, fixed negative potential, a second voltage divider connected with the terminals of the field exciting D. C. source and comprising, in series, a resistance connected with the positive terminal of said D. C. source, a junction and a voltage control tube which maintains a constant voltage drop between the junction in the second voltage divider and the negative terminal of said D. C. source, a field excitation circuit including the positive terminal of said D. C. source, the generator field coil, a second thermionic tube whose plate is connected to the field coil and whose cathode is connected to the junction in the second voltage divider, the voltage control tube and the negative terminal of said D. C. source, a connection between the grid of the second thermionic tube and the junction in the first voltage divider, a potentiometer connected with the rectifier terminal and a fixed potential D. C. source of relatively low voltage whose positive terminal is connected with the potentiometer and whose negative terminal is connected with the grid of the first mentioned thermionic tubes whereby the conductivity of the first thermionic tube is responsive to the relation between rectifier' D. C. terminal voltage and the voltage of the second mentioned D. C. source, whereby the potential at the junction in the first voltage divideraccordingly varies to vary the grid.- bias on the second thermionic tube, and whereby the conductivity of the latter tube varies to change REFERENCES CITED The following references are of record in the file of this patent:.

UNITED STATES PATENTS Number Name Date 2,209,232 Moyer July 23, 1940 2,220,755 Edwards Nov. 5, 1940- 2,251,683 Logan Aug. 5,. 19.41 2,262,359 Exner Nov. 11, 1941 OTHER REFERENCES A. P. C. application of Basili, Serial No. 287,174,.

published May 18, 1943. 

